FIELD OF THE INVENTION

This invention relates to a lightweight drill and more particularly, but not exclusively, to a lightweight hydraulic rock drill.

BACKGROUND TO THE INVENTION

Hand-held hydraulic mine drills exert rotational and percussive forces on a drill steel to drill into a rock face or mine wall, such as a mine hanging wall.

Hand-held hydraulic mine drills include top hammer drills, down-the-hole (DTH) drills and rotary percussion drills.

South African patent number 2022/02598 entitled “Drill” in the name of Sulzer South Africa) Holdings (Pty) Ltd describes a hydraulic rock drill. The drill having a plunger, a rotation means and a plunger actuator for reciprocating the plunger between an extended position in which a front end thereof forces a drill steel to an extended position and a retracted position in which the drill steel is free to move back onto the front end of the plunger, the plunger having plunger engagement formations on an outer surface thereof engaged with complementary rotation means engagement formations on an inner bore of the rotation means, the engagement formations extending at least partially radially from the plunger or from the bore so that movement of the plunger from its retracted position to its extended position causes rotation of the rotation means about its axis in one direction of rotation and thus rotation of the drill steel about its axis by the rotation means.

US patent publication number US20140174779A1 , entitled “High frequency fluid driven drill hammer percussion drilling in hard formations”, filed in the name of Per A. Vatne, discloses a fluid pressure driven, high frequency percussion hammer for drilling in hard formations is presented. A hammer piston of the percussion hammer has a relatively large and longitudinally extending bore that provides minimal flow resistance for a drilling fluid flowing through the bore during the return stroke of the hammer piston. The bore is closeable in the upstream direction by a valve plug that follows the hammer piston during the stroke. The valve plug is controlled by a relatively long and slender valve stem that is mechanically able to stop the valve plug by approximately 75% of the full stroke length of the hammer piston and separates the plug from a seat ring. Thus, the bore opens up such that the bore fluid can flow therethrough, and the inherent tension spring properties of the valve stem returns the valve plug so rapid that it will be good through flow during return of the hammer piston.

US patent number US6454026B1 , entitled “Percussive down-the-hole hammer for rock drilling, a top sub used therein and a method for adjusting air pressure”, filed in the name of Matthew Floyd Shofner and assigned to Sandvik Intellectual Property AB discloses a down-the-hole percussive hammer that includes a cylindrical casing adapted to carry a drill bit, and a piston mounted in the casing for reciprocal movement to repeatedly strike the drill bit. A top sub is mounted at a rear portion of the casing, the top sub including a front face facing the piston. A feed tube is mounted to the top sub and extends forwardly along a centre axis of the casing and defines an air-conducting passage. The piston includes an axial through-hole which slidably receives the feed tube. The front face and the feed tube together define a recess opening toward the piston. A removable volume-changer is insertable into the recess to vary a volume of a space in which the piston slides, and thus control a pressure at which the piston operates.

These drills or drill assemblies are very heavy as the material which it is made of needs to be strong enough to withstand the percussive force required to drill into a rock face or mine wall. The piston, which ultimately drives the drill steel forward needs to be made from a very durable material and is main contributor to the weight of the drill assembly.

For the same reason, the drill assemblies may also be cumbersome as the strong materials take up more space.

As mine workers have to drill in small spaces an low to the ground, this heavy, cumbersome drill assemblies are very difficult to handle. OBJECT OF THE INVENTION

It is an object of this invention to provide a lightweight drill of the type described above which at least partially alleviates the problems described above.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a lightweight drill comprising a piston having a weight of less than 1095 grams.

There is further provided for the piston to have a maximum diameter of 40mm and a minimum diameter of 22.14 millimetres.

The length of the piston is a maximum of 245.4 millimetres.

There is provided for the piston to be connected to a hydraulic power source to enable reciprocal movement of a plunger and/or drill steel.

There is provided for the piston to have a central bore which defines an at least partially hollowed out core.

There is provided for a drill assembly, which the piston forms part of, to have a maximum total combined weight of 18.1 kg. The piston is connected to a plunger, a rotation means and an actuator for reciprocating the plunger between an extended position in which a front end thereof forces a drill steel to an extended position and a retracted position in which the drill steel is free to move back onto the front end of the plunger

The plunger having plunger engagement formations on an outer surface thereof engaged with complementary rotation means engagement formations on an inner bore of plunger, the engagement formations extending at least partially radially from the plunger or from the bore so that movement of the plunger from its retracted position to its extended position causes rotation of the rotation means about its axis in one direction of rotation and thus rotation of the drill steel about its axis by the rotation means.

These and other features of the invention are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention is described below, by way of example only, with reference to the drawings in which:

Figure 1 shows a perspective view of a lightweight drill;

Figure 2 shows a perspective view of the piston; and

Figure 3 shows a side view of the piston; Figure 4 shows various views of the drill; and

Figure 5 shows various views of the piston.

DETAILED DESCRIPTION OF THE DRAWING

With reference to the figures, a lightweight drill is generally indicated by reference numeral 1 .

The drill includes a piston 2 which reciprocatively moves to force a plunger and drill steel to a position in which the drill steel engages a surface to be drilled.

The piston 2 has a leading end 3 which connects to a plunger and a trailing end 4 which connects to a reciprocating hydraulic pressure source which forms part of the drill 1.

A piston 2 plays an integral part in the operation such as rotation, speed and power at which a drill can perform.

The piston 2 has a lighter than usual weight of 1095 grams as opposed to the more conventional weight of 1596 grams. The piston 2 has at its widest point 5 a diameter of 40 millimetres and at its narrowest point 6 a diameter of 22.14 millimetres.

The piston 2 has between its leading end 3 and its trailing end 4 a maximum length 7 of 245.4 millimetres.

The drill assembly 1 was specifically designed to accommodate this, smaller, lightweight piston 2. The drill 2, as such, is also lighter in weight and smaller in size as a cumbersome drill is no longer required to move the size and weight of conventional pistons.

The smaller drill assembly 1 has a total combined weight of 18.1 kg whereas the more conventional drill assemblies have a total combined weight of approximately, or more than 24.4 kg.

The smaller drill assembly 1 can work with water pressure of between 13 and 18 MegaPascal (“MPa”) at a water flow rate of 50 L/min (0.83 L/sec). The drill 2 operates at around 260 revolutions per minute.

The smaller drill assembly 1 has a penetration rate of 1 .3 meters per minute at 110 - 120 Kg thrust and provides energy output of 19.3 kilowatts.

It is envisaged that the lightweight drill described herein will be convenient to use in that it not only weighs less than conventional drills as known in the art, but also smaller is size. This means that it is easier for an operator to operate the drill underground in a mining environment.

It will be appreciated by those skilled in the art that many other embodiments of the invention described above are possible without departing from the scope of the invention.